Congrats on your submission! I think a little bit of tweaking could have made it a bit better. My suggestions would be, keep a score on the top somewhere to give users a goal to try to beat. The other thing would be to have more enemies popping up on the screen at a time after a while. The one enemy at a time kept the pace of the game feeling a bit slow. If you had 1 ship on the screen until 5 ships were destroyed and then having 2 until another 5 were destroyed and then 3 ships at a time, etc. I think you had a good base to build upon to make it better.